A salmonella outbreak caused by the popular Kellogg’s breakfast cereal has grown since it was first reported in June, and has now infected 100 people in 33 states — with at least 30 people hospitalized due to the foodborne illness.

The CDC created a case count map (see full version here) of the Honey Smacks salmonella outbreak, indicating that New York, California, Massachusetts, Pennsylvania, and Virginia have seen the most cases of the illness to date. (Map: CDC)

The Food and Drug Administration reported that despite a voluntary recall by the Kellogg Company in mid-June, recalled boxes of Honey Smacks cereal are still being offered for sale. “Retailers cannot legally offer the cereal for sale and consumers should not purchase Kellogg’s Honey Smacks cereal,” the agency stated on Thursday.

The CDC confirmed that it detected salmonella in samples of Honey Smacks. “Do not eat recalled Kellogg’s Honey Smacks cereal in any size packaging,” the agency stated. “Check your home for the recalled cereal and throw it away, or return it to the place of purchase for a refund.”

The Kellogg Company, which makes Honey Smacks, specifically recalled 15.3- and 23-ounce packages of the cereal. The recalled boxes have a “best if used by” date of June 14, 2018 through June 14, 2019; the 15.3-ounce size has a UPC code of 38000 39103, and the 23-ounce size has a UPC code of 38000 14810. Kellogg said in a June press release that the company has launched an investigation with the third-party manufacturer that produces Honey Smacks. A publicist for Kellogg’s told Yahoo Lifestyle that any packages of the cereal on the market should be discarded.

Salmonella is responsible for about 1.2 million illnesses, 23,000 hospitalizations, and 450 deaths in the U.S. each year, and food is the source of about 1 million of those illnesses, the CDC says. Most people who contract the infection develop diarrhea, a fever, and stomach cramps about 12 to 72 hours after they’ve been infected, and they’re usually sick for four to seven days. While most recover without any treatment, some people may have diarrhea so severe they require hospitalization, the CDC says. People who are immunocompromised, elderly, or very young (who are the most likely to be eating this cereal) are most at risk of complications, food safety expert Darin Detwiler, director of the Regulatory Affairs of Food and Food Industries program at Northeastern University, tells Yahoo Lifestyle.

How can cereal carry salmonella?

Salmonella is usually linked to things like raw meat and dairy products, so it’s a little confusing for it to show up in a dry cereal. This isn’t common at all, but it happens, Felicia Wu, a professor in the Department of Food Science and Human Nutrition at Michigan State University, tells Yahoo Lifestyle. “Typically, American breakfast cereals are considered dry products, thus not considered a source of bacterial contamination,” she says.

But several strains of salmonella have evolved and developed an ability to tolerate dry environments, though they needed moisture to survive in the past, Wu explains. Other possible ways salmonella might have gotten into the cereal: The product could have higher moisture levels normal for breakfast cereal, or there could have been cross-contamination of any of the ingredients used to make the cereal. “If any one of those ingredients become contaminated, the whole lot does,” Detwiler says. Dry cereals are also more likely to sit on shelves for long periods of time, giving pathogens more time to grow, he points out.

Especially concerning for kids

This outbreak is especially concerning given that kids are most likely to eat the cereal and they can get really sick from it. It’s also concerning that children are often given foods like crackers and cereal when they have upset stomachs — and if they’re given contaminated cereal, they can get even sicker, Detwiler noted.

It can be hard to distinguish a salmonella infection from any other stomach bug a child may have, but salmonella infections almost always come with a fever while gastroenteritis may or may not, Danelle Fisher, MD, chief of pediatrics at Providence Saint John’s Health Center in Santa Monica, Calif., tells Yahoo Lifestyle. “It’s also quite common for the diarrhea to be bloody with a salmonella infection,” she says. While it’s possible to have salmonella without bloody diarrhea, seeing it should be a tip-off that your child is struggling with it, she says.

If you suspect that your child has a salmonella infection, call the child’s pediatrician immediately and have him or her evaluated. Dehydration is a big concern, as is a bloodstream infection in younger children, Fisher says.

Unfortunately, there’s no way to know in whether your cereal has salmonella in it, Detwiler says. But outside of this recall, parents shouldn’t be especially worried about their child contracting salmonella from dry cereal, Wu says. “Salmonella contamination of dry breakfast cereals has been a very uncommon occurrence,” she says.